This research project is designed to utilize micropuncture methods to examine the effects of ischemic acute renal failure on parameters of nephron function including single nephron glomerular filtration rate, tubular pressure, glomerular capillary pressure, effective filtration pressure, the ultrafiltration coefficient, and afferent and efferent arteriolar resistances. All measurements listed above will be made in dogs during a control period and then, where possible, at 1, 2, 3 and 24 hrs after completion of a 40 min infusion of norepinephrine (0.75 micron g/kg/min) into the left renal artery. Because various vasodilators and diuretics have been used to reduce the severity (decreased CIn) of this form of acute renal failure, other dogs will be treated with mannitol and furosemide and repeat measurements of the above parameters will be performed. Experiments will also be conducted in dogs treated with prostaglandin E and bradykinin. Hopefully these measurements will permit the demonstration of the mechanism and site at which these agents alleviate the severe decrease in CIn. Bilateral acute renal failure will be created by infusing norepinephrine into both kidneys. Repeat studies of nephron and whole kidney function will be undertaken to compare the responses to protective agents in this model vs. the responses in the unilateral model.